Adding liquids, such as water or water vapor, to the induction system of an internal combustion system is an idea which is in itself quite old. However, the comprehension of the full benefits to be obtained by proper regulation of the amount of added liquid (along with a proper amount of associated heat energy) at all conditions of engine operation have been lacking; and the prior art apparatus and techniques for adding liquid have been inadequate to fully accomplish all the desired results.
The engine needs different amounts of fluid at varying conditions of operation of the engine. The engine's need for fluid at any particular condition of operation is dependent on the amount of fluid which will produce the best engine operation at that condition. The best engine operation includes obtaining complete lean, clean combustion with the lowest emissions of HC, CO and NO.sub.x and best fuel economy without detonation, pre-ignition, or after fire (dieseling). The engine's need for fluid varies widely from no fluid at all under certain conditions of operation to amounts of fluid flow in the same order of magnitude of fuel flow at other conditions of engine operation. For example, the engine's need for fluid is zero at engine shut-off as no liquid can be permitted to flow into the engine when the engine is shut off. If the liquid flow into the engine were to be permitted at shut-off, corrosion and/or liquid lock will occur.
At normal, steady-state, low-speed idle, only a trace amount of fluid, or no fluid at all, is required to give optimum low idle emissions.
Increasing quantities of fluid proportionate to power are required as engine power is increased at each steady state point.
Under dynamic conditions, such as, for example, acceleration at high BMEP, an extra amount of fluid is required over and above operation at a steady state condition; and, in the case where the fluid is steam, the steam should be of a lower quality, that is, with a certain percentage of water droplets carried with the steam (in order to give maximum combustion cooling) to keep nitrous oxide emissions within satisfactory limits.
On deceleration, less fluid is required at each point in the deceleration than would be desired for operation at a steady state at any point (zero fluid at zero throttle deceleration).
The engine's need for fluid is also determined by limiting the fluid to an amount that will not hurt the combustion. For instance, in deceleration, if fluid is not limited, too much fluid can be introduced to cause the combustion to be poor. This will produce incomplete combustion and will cool the flame sufficiently that undesirable amounts of HC and CO will be produced. Engine efficiency can be seriously impaired. Hydrocarbon deposits also increase.
On acceleration, the engine's need for fluid is dependent on introducing the right amount of fluid to absorb, by its high specific heat plus latent heat of evaporization of liquid droplets included (water droplets in the case of steam) plus heat of dissociation, excess engine heat generation, which would otherwise go toward producing high combustion and surface peak temperatures and peak pressures at about top dead center (but this still must be done without introducing too much fluid so as to impair combustion with the undesirable effects noted above). By introducing the right amount of additional fluid, the energy is absorbed as energy in steam (in the case where the fluid is water) which is given back during the latter part of the cycle as expansion of the steam. This adds smoothly at favorable crank angle to the power stroke and torque of the engine. The right amount of additional fluid at this point, therefore, prevents hot spots and smooths the pressure and temperature and energy conversion.
Also, the right amount of fluid needs to be introduced to provide for engine cleanliness. The right amount of fluid will provide both clean combustion and removal of engine deposits.
Further, it is needed to inject the right amount of fluid and heat in order to heat and thereby to vaporize the fuel to give equal fuel-air ratio distribution and mass distribution between the cylinders. This gives maximum economy and lowest emissions.
Extra charge density can be provided by introducing fluid droplets in the fuel-air mixture charge at full throttle or high power operation. The fluid droplets, if introduced into the cylinder at the proper time before valve closure, cool the charge so as to increase the charge density before the valve closure, and thus, in effect, provide a form of supercharging.
Other inventors have not recognized these problems and have not implemented any control mechanism effective to produce the benefits which can be obtained by controlling the amount of added fluid and heat energy in response to engine need at each condition of operation of the engine.
Prior attempts to introduce fluids into the engine have relied primarily on intake manifold vacuum as the driving force to induce liquid flow. This has the disadvantage of having the greatest vacuum (and hence the larger driving force for liquid flow) at the conditions when the engine needs the least or no addition of liquid (throttle closed). In addition when the engine requires the greatest liquid flow (acceleration or heavy load) manifold vacuum is at a minimum. This present invention uses venturis, ejectors and vortex tubes in such combination to provide liquid flow when needed by the engine and not necessarily when most easily injected using intake manifold vacuum.
It is a primary object of the present invention to control the added amount of fluid and heat energy in relation to engine need at all conditions of operation of the engine to obtain the benefits as described above.